Mobile communication transceivers, for example a mobile telephone, generally comprise a single frequency-synthesizer which serves as a local oscillator for both the transmit and receive sides of the transceiver. Such frequency-synthesizers typically comprise one or more phase-locked loops (PLLs) that can be programmed to lock onto a specific frequency.
In a dual standard phone, for example one that is capable of working in both a WCDMA environment (Wideband Code Division Multiple Access) and a GSM environment (Global Standard for Mobile communication), it is likely that two separate radio frequency (RF) sections will be required. Following conventional design procedures, each RF section would incorporate a respective frequency synthesizer and the two RF sections would be required to operate in close proximity to each other.
The frequency synthesizer of one RF section will be a possible source of RF interference to the other RF section, and likewise the other RF section will be a possible source of interference to the one section. One method to alleviate this contribution of mutual interference is to turn off each PLL when it is not in use. Unfortunately, returning the synthesizer to its steady state mode of operation takes time and there is therefore a delay between turning the synthesizer back on and being able to work. This time delay may be detrimental to the operation of the dual standard phone.
In a dual standard phone it is not unusual to have to pause operation in one standard (e.g. WCDMA) while measurements are made of the system in the other standard (e.g. GSM). If this pause in operation is too long the interruption can become perceptible to the user. Plainly this is undesirable because the quality of service is degraded. Indeed, if the pause is too long, the phone may find itself disconnected from the original service. Under these circumstances, the economic value of a multiple standard phone is severely reduced.
Additionally, power consumption in mobile communication transceivers is a continuing concern for designers and developers. Reductions in power consumption directly contribute to the usefulness of mobile phones.
The invention was made with the above discussed problems in mind and aims to address the related problems.